This application is a national stage application of international application PCT/DE03/01671, filed May 23, 2002, which is incorporated by reference in its entirety herein.
1. Field of the Invention
The present invention relates to a shut-off fitting that includes a housing that is connected to an adjacent pipeline and at least one closing body for the pipeline which can be displaced between an open position and a closed position.
2. Background of the Invention
Preferably, such shut-off fittings should require little maintenance and should resist corrosion. They could be made of metal or plastic whereby fittings made of thermoplastic materials have the advantage that the housing parts can be joined using not only commonly used welding methods but also mirror heating element joint methods or heater coil welding techniques. The joint could also result using attachment to an already existing PE pipe network.
Metallic shut-off fittings in the prior art often experience corrosion and severe incrusting when used in drinking water networks. This corrosion or incrusting could lead to operating trouble, such as leakage and damage to the shut-off fitting. In particular, metallic shut-off fittings often suffer sever corrosion due to the heavy weight and mechanical attachment, usually by means of a flanged port fitted with screws, especially when used underground.
Tight closing shut-off fittings used in many different processes even under high pressure and high temperature can be well preserved. Most devices utilize closing bodies which move about an axis laterally to the flow and flows around in the open position.
DE 10 13 135 relates to a high pressure non-return valve made of forging steel which in a fitting inside the pipe can be swiveled about an axis fitted on the outside of the tubular passage in such a way that the tubular passage is opened. While closed, the valve or the closing body lies axially on a circular carrying surface fitted in the tubular passage.
GB 2 009 877 relates to a pipe fitted with two set apart closing valves which basically form a further developed non-return valve. One of the valves is kept in the closed position by a stopping mechanism.
U.S. Pat. No. 4,064,916 relates to a deformable blocking blister which can be moved through the tubular passage by means of cable feeding.
Some uses, in particular when relatively small pipe diameters are utilized, such as in the drinking water area, a shut-off body, will interfere with the flow. It is not possible to lead a go-devil through the pipe either, not even in the open position.
It is thus the object of the invention to provide a shut-off fitting made of thermoplastic material that can be reinforced if necessary so that the disadvantages of the well-known metallic gate valves are avoided.